1. Field of the Invention
The presnet invention relates to an endless transmission belt, particulary to the belt for continuously variable transmission in which the belt is fitted around a primary and a secondary pulley comprising a pair of sheaves. In detail the present invention relates to an endless transmission belt known as a chain type in which many link plates are linked endlessly by pins, and V-blocks as frictional transmitting elements are respectively sustained between pins.
2. Description of the Prior Art
As shown in the Japanese patent publication No. 60-104824, a V-block used in the endless transmission belt has inclined sides partially or entirely contact a pair of sheaves. The front view of the V-block is trapezoidal, and the center portion of the V-block has an opening to retain link plates.
In the prior art mentioned above, a pin connecting the link plates is supported in the vicinity of the right and left side of the V-block, and the pins and the link plates are connected in the center of the V-block. Because of this structure the force transmitted from the V-block to the link or vice versa gives large bending moment to the pins, so excentric wear on the pin or the link may occur. Furthermore as the V-block is rigid against compressive direction of the sheaves, the V-block contacts the sheaves in point or quite small area due to dimensional error on the sheaves or the V-block, and at the portion where the V-block is led to the pair of sheaves, this causes skid and insufficient torque transmission because many V-blocks can not contact the sheaves evenly and accordingly only some of them share the torque.
Then the applicant proposed the endless transmission belt (refer to Japanese Patent Application No. 61-260760) as follows:
"The endless transmission belt has many link plates laminated and connected by pins and has first and second V-blocks whose front views are trapezoidal and which are laid between pins, and contact such pins. On each first and second V-block, an opening is made to contact the pair of sheaves, and a center opening is made to lay the links which are divided into three rows. (unqte)"
The above endless transmission belt has such merits as: during torque transmission the pins are not bent in bow shape and accordingly the load applied to the link plates is averaged and partial wear of the link plate and the exentric waer of the pins are prevented because during torque transmission, at three points along the pin length the pins and the link plates contact so that the torque transmission is not concentrated.
However the above endless transmission belt has such demerit as:
When the V-block is held by the sheaves it is difficult to deform the upper and lower portions of the V-block horizontally because the structure of the V-block is that the front view is near trapezoidal, the upper and lower portions are connected by the two pillar portions, and each corner is rounded to prevent stress concentration but the radius is small; due to this the contact pressure between the V-block and the sheaves becomes very high, and further the contact has to be conducted in quite small area such as a point-contact unless each V-block is made precisely in dimensions; and uneven contact between the V-block and the sheave may cause destruction of the V-block.
Then the present invention is directed to provide the endless transmission belt having the V-block which is easy to be bent horizontaly so that durability is enhanced in addition to preventing the wear of the link plate and the pins.